x86/fpu: Factor out memset(xstate, 0) in fpu_finit() paths

oleg-nesterov · Ingo Molnar · commit 1d23c4518b1f · 2015-03-10T07:14:31.000+01:00
fx_finit() has two users but only fpu_finit() needs to clear xstate, alloc_bootmem_align() in setup_init_fpu_buf() returns zero-filled memory. And note that both memset()'s look confusing. Yes, offsetof() is 0 for ->fxsave or ->fsave, but it would be cleaner to turn them into a single memset() which zeroes fpu->state. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Rik van Riel <riel@redhat.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Tavis Ormandy <taviso@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1425967585-4725-2-git-send-email-bp@alien8.de Link: http://lkml.kernel.org/r/20150302183257.GC23085@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
@@ -135,7 +135,6 @@ static __always_inline __pure bool use_fxsr(void)
 
 static inline void fx_finit(struct i387_fxsave_struct *fx)
 {
-	memset(fx, 0, xstate_size);
 	fx->cwd = 0x37f;
 	fx->mxcsr = MXCSR_DEFAULT;
 }
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
@@ -224,11 +224,12 @@ void fpu_finit(struct fpu *fpu)
 		return;
 	}
 
+	memset(fpu->state, 0, xstate_size);
+
 	if (cpu_has_fxsr) {
 		fx_finit(&fpu->state->fxsave);
 	} else {
 		struct i387_fsave_struct *fp = &fpu->state->fsave;
-		memset(fp, 0, xstate_size);
 		fp->cwd = 0xffff037fu;
 		fp->swd = 0xffff0000u;
 		fp->twd = 0xffffffffu;

Original file line number	Diff line number	Diff line change
`@@ -135,7 +135,6 @@ static __always_inline __pure bool use_fxsr(void)`
`135`	`135`
`136`	`136`	`static inline void fx_finit(struct i387_fxsave_struct *fx)`
`137`	`137`	`{`
`138`		`- memset(fx, 0, xstate_size);`
`139`	`138`	`fx->cwd = 0x37f;`
`140`	`139`	`fx->mxcsr = MXCSR_DEFAULT;`
`141`	`140`	`}`